Acoustic echo is a common problem with full duplex audio system(s), for example, audio conferencing systems and/or speech recognition systems. Acoustic echo originates in a local audio loop back that occurs when an input device, such as a microphone, picks up audio signals from an audio output device, for example, a speaker, and sends it back to an originating participant. The originating participant hears this acoustic echo of the originating participant's own voice as the other participant speaks.
For example, consider the instance in which a first participant at a first physical location with a microphone and speaker and a second participant at a second physical location with a microphone and speaker are taking part in a call or conference. When the first participant speaks into the microphone at the first physical location, the second participant hears the first participant's voice played on speaker(s) at the second physical location. However, the microphone at the second physical location can pick up and transmit the first participant's voice. The first participant can then hear an echo of the first participant's voice with a slight delay due to the round-trip transmission time.
Acoustic echo can be caused or exacerbated when sensitive microphone(s) are used, microphone and/or speaker analog volume is turned up high, and/or the microphone and speaker are physically in close proximity to one another. In addition to being annoying, acoustic echo can prevent normal conversation among participants in a conference, or prevent normal operation of an automatic speech recognition system.
Conventionally, acoustic echo was reduced using audio headset(s) that prevent an audio input device (e.g., microphone) from picking up the audio output signal. Additionally, special microphones with echo suppression features were utilized. However, these microphones are typically expensive as they contain digital signal processing electronics that scan the incoming audio signal and detect and cancel acoustic echo. Acoustic echo can also be reduced by acoustic echo cancellation component(s); however, with the wide variation of audio input device and audio output devices, effective acoustic echo cancellation can be difficult and result in a frustrating experience for end user(s).